1. Field of the Invention
The present invention relates to camera bodies having a function of correcting image blur and camera systems including the camera bodies. The invention is suitable for image pickup apparatuses such as video cameras and digital cameras.
2. Description of the Related Art
Automation of image pickup apparatuses such as digital cameras and video cameras has been progressing, and many of them include, for example, an automatic focusing function and an automatic exposure compensation function.
Furthermore, many recent image pickup apparatuses include image-blur correcting units that automatically correct blur in images caused by vibration. Moreover, some image pickup apparatuses include a hybrid image-blur correcting system so as to efficiently correct image blur using a plurality of image-blur correcting units of different types.
According to a technology described in U.S. Pat. No. 5,657,080 in which image blur is corrected using both an optical image-blur correcting unit and a digital image-blur correcting unit, the optical image-blur correcting unit or the digital image-blur correcting unit is selected in accordance with the frequency of the image blur.
According to a technology described in U.S. Pat. No. 5,867,213, an optical image-blur correcting unit or a digital image-blur correcting unit is selected in accordance with the zooming position of an imaging optical system. Furthermore, the optical image-blur correcting unit or the digital image-blur correcting unit is selected in accordance with values of high-frequency components in image signals.
According to a technology described in Japanese Patent Laid-Open No. 10-56592, image blur is divided into components of two directions orthogonal to each other on a plane orthogonal to the light axis, and the two components are separately corrected using a digital image-blur correcting unit and an optical image-blur correcting unit. Furthermore, the optical image-blur correcting unit is used in combination with the digital image-blur correcting unit when the correction area of the digital image-blur correcting unit becomes deficient.
In general, many portable image pickup apparatuses such as video cameras and digital cameras include a plurality of image-blur correcting units. The portable image pickup apparatuses use one or more image-blur correcting units for correcting image blur caused by a camera shake during capturing of moving images and during monitoring of object images. Such image pickup apparatuses have been strongly required to have a high correcting effect of image blur and to have a small imaging optical system for high portability.
An optical image-blur correcting unit includes an afocal lens system that bends the light axis, a variable apex-angle prism, and driving mechanisms and position detecting mechanisms for these components. When only the optical image-blur correcting unit is used for obtaining a sufficient correcting effect of image blur, the structure of the optical image-blur correcting unit becomes complex, and the outer dimensions of the imaging optical system can be increased.
Moreover, when only a digital image-blur correcting unit is used for obtaining a sufficient correcting effect of image blur, an image pickup device that is larger than usual is required, and the size of the imaging optical system can be increased in accordance with the size of the image pickup device. When the imaging optical system includes a zoom lens, the correction area of the image pickup device is proportional to the focal length at the telephoto side. Therefore, when a sufficient correction area for correcting image blur is not ensured, image blur is unnaturally corrected, and images can become degraded.
When a large degree of image blur is simply corrected using the optical image-blur correcting unit and the digital image-blur correcting unit, the size of the imaging optical system can be increased. Moreover, the state of blur occurring in images widely varies in accordance with types of vibration applied to the image pickup apparatus, for example, continuous or discontinuous, the amplitude of, for example, angular acceleration, and the magnitude of vibration frequency (high or low).